Exploring generic principles of compartmentalization in a developmental in vitro model.

Self-organization of cells into higher-order structures is key for multicellular organisms, for example via repetitive replication of template-like founder cells or syncytial energids. Yet, very similar spatial arrangements of cell-like compartments ('protocells') are also seen in a minimal model system of Xenopus egg extracts in the absence of template structures and chromatin, with dynamic microtubule assemblies driving the self-organization process. Quantifying geometrical features over time, we show here that protocell patterns are highly organized with a spatial arrangement and coarsening dynamics similar to that of two-dimensional foams but without the long-range ordering expected for hexagonal patterns.

Quantifying active diffusion in an agitated fluid.

Mixing of reactants in microdroplets predominantly relies on diffusional motion due to small Reynolds numbers and the resulting absence of turbulent flows. Enhancing diffusion in microdroplets by an auxiliary noise source is therefore a topical problem. Here we report on how the diffusional motion of tracer beads is enhanced upon agitating the surrounding aqueous fluid with miniaturized magnetic stir bars that are compatible with microdroplets and microfluidic devices.

Miniaturized magnetic stir bars for controlled agitation of aqueous microdroplets.

Controlled stirring of tiny volumes of aqueous fluids is of particular importance in the life sciences, e.g. in the context of microfluidic and lab-on-chip applications.

Chladni Patterns in a Liquid at Microscale.

By means of ultrathin silicon membranes excited in the low ultrasound range, we show for the first time that it is possible to form two-dimensional Chladni patterns of microbeads in liquid. Unlike the well-known effect in a gaseous environment at the macroscale, where gravity effects are generally dominant, leading particles towards the nodal regions of displacement, we show that the combined effects of an ultrathin plate excited at low frequency (yielding to subsonic waves) together with reduced gravity (arising from buoyancy) will enhance the importance of microstreaming in the Chladni problem. Here, we report that for micrometric beads larger than the inner streaming layer, the microscale streaming in the vicinity of the plate tends to gather particles in antinodal regions of vibrations yielding to patterns in good agreement with the predicted modes for a liquid-loaded plate.

Transient behavior and relaxation of microcapsules with a cross-linked human serum albumin membrane.

Capsules consist of droplets enclosed by a membrane with shear resistant properties especially when fabricated by interfacial cross-linking. In many applications, the protection and release of the internal medium need to be strictly controlled. It is possible to tune the membrane mechanical properties by changing the physico-chemical conditions of the fabrication process, but a good control of the production requires their characterization, which is a scientific challenge, since the objects are a few tens of microns in size at most.

Hydrodynamic interaction between two vesicles in a linear shear flow: asymptotic study.

Interactions between two vesicles in an imposed linear shear flow are studied theoretically, in the limit of almost spherical vesicles, with a large intervesicle distance, in a strong flow, with a large inner to outer viscosity ratio. This allows to derive a system of ordinary equations describing the dynamics of the two vesicles. We provide an analytic expression for the interaction law.

Hepatic extraction, metabolism, and biliary excretion of irinotecan in the isolated perfused rat liver.

Irinotecan (CPT-11) is a semisynthetic derivative of camptothecine that has proved activity in the treatment of colorectal carcinoma. The metabolites identified in humans include SN-38, SN-38 glucuronide, and several CYP3A-derived metabolites. We have studied the hepatic extraction, metabolism, and biliary excretion of irinotecan in the isolated perfused rat liver.

Hepatic disposition and toxicity of cationized goat immunoglobulin G and fab fragments in isolated perfused rat liver.

Colchicine-specific goat IgG and Fab fragments were cationized by covalent coupling of hexamethylenediamine. The immunoreactivity of antibodies was not changed following cationization. The interaction of 125I-radiolabeled native (nIgG and nFab) and cationized immunoglobulin G (cIgG) and Fab fragments (cFab) with liver was investigated using isolated perfused rat liver (IPRL) and isolated rat hepatic parenchymal cells (PCs) and nonparenchymal cells (NPCs) in suspension.

The anti-cancer drug 5-fluorouracil is metabolized by the isolated perfused rat liver and in rats into highly toxic fluoroacetate.

We report the first demonstration of the biotransformation of the anti-cancer drug 5-fluorouracil (FU) into two new metabolites, alpha-fluoro-beta-hydroxypropionic acid (FHPA) and fluoroacetate (FAC), in the isolated perfused rat liver (IPRL) and in the rat in vivo. IPRL was perfused with solutions of pure FU at two doses, 15 or 45 mg kg(-1) body weight, and rats were injected i.p.

Immunoglobulin G, F(AB')2, and fab fragment uptake kinetics in isolated perfused rat liver and rat hepatic cells.

The interaction of 125I-radiolabeled immunoglobulin G (IgG), F(ab')2, and Fab fragments with different modes of production (polyclonal or monoclonal), belonging to different subclasses (IgG1 and IgGT) and derived from different sources (mouse, rat, and horse) with liver, was investigated by using isolated perfused rat liver and isolated rat hepatic parenchymal cells (PCs) and non-parenchymal cells (NPCs) in suspension. Lactosaminated-bovine serum albumin (Lac-BSA) and formaldehyde-bovine serum albumin were used as markers of specific binding to PCs and NPCs, respectively. Using the isolated perfused rat liver model, data clearly indicated a very weak hepatic extraction ratio (< 0.

Effect of colchicine-specific Fab fragments on the hepatic clearance of colchicine.

The influence of colchicine-specific Fab fragments on hepatic metabolism and biliary excretion of colchicine was studied in the isolated perfused rat liver. Isolated rat livers were perfused for 180 min with either [3H]colchicine (initial concentration: 50 ng/ml) or Fab-[3H] colchicine in a stoichiometrical proportion at a constant flow of 100 ml/min in a recirculating system. Based on perfusate concentrations, the hepatic extraction ratio of colchicine was more than 15-fold decreased when colchicine was bound to Fab fragments (E = 0.

[Adaptation of an A.G.S. endo-uterine catheter for hysterographic examination during radium therapy (author's transl)].

The authors propose an endo-uterine catheter which will permit a hysterographic examination to be made during utero-vaginal radium therapy, thus making it possible to check: --that the catheter has advancec correctly after insertion; --that the uterine cavity intact: --that the catheter is in the correct place; --its retention during treatment. By using radio-opaque rings and small balloons in the hysterographic examination, it is possible to locate: --the external orifice of the cervix; --the urethral meatus; --the anterior wall of the rectum and the posterior wall of the bladder. In this way, the target volume is loated with precision, and the length, position and activity of the various radio-active sources can be adapted accordingly.